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90 5351 AC Problems

1K views 13 replies 5 participants last post by  SharkmanBMW 
#1 ·
I need some help here. My ac will only come on for a minute then turns off, a few minutes later it comes on the same thing. Here is what I have done so far. Replaced dryer, pressure switches, and expansion valve, converted to r134(removed ac compressor and drained the put in 5oz of Pag oil) and replace aux low speed resistor. I vacuum system down for 4 hours and check to see if it holds. Check good. If I supply power to the compressor directly it works fine and cools great. I have check all relay and fuses. Sometime it will stay on for five minutes and cools great. The Bently manual refers to a ac compressor clutch control relay which I cannot find. My car was built 8/90. Any Ideas???

Chris
 
#2 ·
This is a tough one. since you have replaced a lot of AC parts and still cannot find the problem, i would take it to a dealer and see what they have to say. i think i remember reading somewhere that there is a setting on the onboard comptuer that can change the amount of time the AC is on for. try resetting it. it should say how to reset the onboard computer in the Bentley manual. when you supply power directly to the compressor, you are bypassing the onboard comptuer.

Also, it could be your battery that is going bad. make sure the output voltage of your battery is correct.
 
#4 ·
Thanks will try checking the evap temp sensor, though I am not looking forward to taking the console and dash apart again. Also just replace battery a few monthe ago. When you say reset the on board computer does that happen when the battery is disconnected? I had the battery disconnected when I change the expansion valve.

Chris
 
#7 ·
I wasn't to bad. I used a Bently manual which help. I had to pull the radio, glove box, the shift knob, center console, and panels under the steering wheel. Then there are clips and two screws that hold the evap cover on. It took about a hour.
 
#11 ·
AC Fix

I wanted to thank everyone for there ideas. I fix it!! I check the evaperator sensor and it was bad went to the local junk yard and found one on the same year car. I had my mutimeter with me and it check good, so installed and still no A/C. Disconnected the battery and keep it off for hour no luck. So I check the compressor cut off relay located behind the left hand kick panel. I Had power to relay, but change anyway. I was one of those orange relay which are everywhere on the car had a spare and Bingo A/C works

Thanks

Chris
 
#14 ·
cga said:
I wanted to thank everyone for there ideas. I fix it!! I check the evaperator sensor and it was bad went to the local junk yard and found one on the same year car. I had my mutimeter with me and it check good, so installed and still no A/C. Disconnected the battery and keep it off for hour no luck. So I check the compressor cut off relay located behind the left hand kick panel. I Had power to relay, but change anyway. I was one of those orange relay which are everywhere on the car had a spare and Bingo A/C works

Thanks

Chris

for the record, instead of disconnecting the battery for an hour, you can jump the pos. & neg. cables together to "reboot" the computers in an E34.

1. disconnect battery cables, first -, then +
2. turn ignition on position II
3. connect both battery cables ("short") for at least 10 minutes for drain of remaining power out of the system
4. ignition off
5. connect battery cables again to battery, first +, then -

all computers will start with their basic programming and will "adapt" from there. credit to "shogun" for the procedure.
 
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